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EEWR Brown Bag Seminar wtih Xinyi Shen and Rui Wang, Graduate Students

Speaker: Xinyi Shen and Rui Wang, Graduate Students
Series: EEWR Brown Bag Seminars
Location: Engineering Quad E225
Date/Time: Friday, November 16, 2018, 12:00:00 p.m. - 01:00:00 p.m.


Free Energy of Interaction of Two Smectite Clay Nanoparticles in Liquid Water
Speaker: Xinyi Shen

Xinyi ShenClay minerals are one of the most important constituents of soils, sediments, and sedimentary rocks. The aggregation and swelling of clay nanoparticles, strongly influence porosity and permeability and is highly sensitive to both and long-range geochemical interactions. Simulation predictions of clay aggregation and swelling, to date, have relied almost exclusively on coarse-grained simulation technique that rely on effective inter-particle potential models. Most such models are based on the DLVO theory of long-range colloidal interactions and they neglect the short-range interactions. All-atom molecular dynamics (MD) simulations have focused almost exclusively on the crystalline hydrates. To bridge this gap, our research uses all-atom MD simulations to examine the energetics of a pair of smectite clay nanoparticles suspended in bulk liquid water. We use the metadynamics  methodology to elucidate the free energy landscape over a range of  interparticle distances that includes the transition between crystalline and  osmotic swelling. Different solutions are used to study the effect of water  chemistry.

Ammonia Seasonality Study based on Different Land Use
Speaker: Rui Wang

Rui WangGas phase NH3 is a critical aerosol precursor species and a key component  of nitrogen deposition in sensitive ecosystem. The major NH3 source is agriculture, mainly from volatilization of livestock waste and fertilizers, which are hard to estimate due to the lack of agricultural activity database, e.g. fertilization time database. Besides, NH3 emissions are subject to considerable uncertainties partly due to the extreme difficulty of measuring gas phase NH3. Recently, satellites measurements have been developed to provide insights on NH3 distributions on a global and daily scale. A high resolution (0.02°×0.02°) NH3 map in contiguous U.S. was developed by oversampling Infrared Atmospheric Sounding Interferometer (IASI) NH3 column data, providing information on the magnitude and spatiotemporal variability of NH3. Combined with cropland use data, the map was used to study the NH3 seasonality in areas with different land use type and compared with the NH3 emission inventories, which can help constrain the current NH3 emission inventory.